In recent years, the technique of equipping a positioning function unit in a mobile terminal device as represented by, for example, a mobile telephone is becoming widely used.
In such a positioning function unit in the above-described mobile terminal device, a technique of selectively applying a different positioning method depending on the situation is employed.
At present, as positioning methods applied to the mobile terminal devices, there are a navigation message (such as Almanac and Ephemeris) held on the network side, the GSP time, A-GPS positioning operation by using assist information including outline location information and the like of the mobile terminal device, and autonomous GPS positioning operation for all of the positioning operations on the mobile terminal device side by receiving the positioning information from a GPS satellite without using the above-described assist information.
Specifically, the A-GPS positioning operation is a positioning method of network support type by using the assist information from the network side. The A-GPS positioning operation includes: a so-called UE-Assisted (or MS-Assisted) method in which a positioning server on the network performs processes including the final positioning operation process, and supplies results of the positioning operation process to the mobile terminal device; and a so-called UE-Based (or MS-Based) method in which the mobile terminal device performs the GPS positioning operation process by using the assist information acquired from the network.
Therefore, various technical proposals has already been made for improving specific functions, such as a reduction in the communication costs or availability of positioning operation under various environments, by adaptively switching the above-described multiple positioning methods.
For instance, in the network support type positioning system, the mobile terminal device needs to acquire the assist information via networks whenever it performs the positioning operation. However, since the traffic is increased for acquiring the assist information and the communication costs are increased, there is a proposal for a technique of focusing on such problems (for instance, see Patent Document 1).
In Patent Document 1, in order to reduce the communication costs, how the frequency of communication for acquiring the assist information is reduced is regarded as an importance issue. Accordingly, there is a proposal of reducing the communication costs of the network support type GPS terminal, by reducing the frequency of communication with the networks as much as possible even for acquiring the outline location state.
That is, in-area cell information, related to the outline location of the mobile terminal device, received by a communication unit in the first GPS positioning operation, is stored in a storage unit. In the second or later GPS positioning operation, only when the in-area cell information stored in the storage unit is different from that of the previous GPS positioning operation, the outline location information is acquired from the network. Then, the acquired outline location information is used for the GPS positioning operation and also stored in the storage unit. In the second or later GPS positioning operation, when the in-area cell information stored in the storage unit is same with that of the previous GPS positioning operation, the outline location stored in the storage unit is used for the GPS positioning operation, so that the frequency of acquiring the outline location information is reduced. As a result, the frequency of communication is reduced to reduce the communication costs.
In addition, there is a proposal for a technique in which multiple positioning methods are made selectively available. Even if one positioning method fails, another positioning method is selected so that an available method is used according to the condition to avoid the situation where the positioning operation is unavailable (for instance, see Patent Document 2).
In the mobile terminal device of Patent document 2, when the network support type positioning operation fails and the location information of the cell where the mobile terminal device is located is acquired in the course of positioning operation, supplementary cell ID positioning operation that is the positioning method of using this location information is performed to avoid the situation where the positioning operation is unavailable.
Additionally, in Patent Document 2, the network support type positioning operation has an advantage that the positioning time is short. However, data communication is needed for acquiring the information that is to be acquired. This causes a problem of placing increased burdens of the communication fees on users. Besides, there is a problem in that the GPS positioning operation cannot be performed in the area where the data communication is unavailable. Patent Document 2, however, discloses that the supplementary cell ID positioning operation can address the both problems.
Meanwhile, in recent years, a mobile communication system is operating for regularly and automatically acquiring in a background process positioning data that are the results of the GPS positioning operation process on the mobile communication device by use of the assist information, and notifying the acquired positioning data to a communication operator or a content delivery operator (for example, see Non-Patent Document 1).
In such a mobile communication system described in Non-Patent Document 1, a so-called push type information delivery service is provided such that the communication operator or the content delivery operator figures out the location of the mobile terminal device based upon the notified positioning data and delivers weather forecasts or town event information in accordance with the location of the current time.
In the mobile terminal device to which the above-described information delivery service by use of the positioning data is made available, while the GPS positioning function is equipped therein, it is devised such that the power consumption needed for the GPS positioning operation can be suppressed as much as possible.
That is to say, the mobile terminal device is provided with an acceleration sensor (walking detecting unit) or a detecting function unit for detecting an in-area sector ID corresponding to the located in-area. Those units acquire the information on the moving status of the mobile terminal device or the in-area history thereof in order to save the power by the frequency of operation of the GPS positioning operation.
This power-saving method will be described specifically as follows. Firstly, as a precondition of applying this method, basically, the GPS positioning operation is continuously performed on a regular basis. In this situation, in the procedure of the GPS positioning operation performed on a regular basis, the positioning operation is repeatedly performed on a predefined period defined by the time-keeping means of the mobile terminal device.
At the starting point of the positioning operation, a data processing engine of the mobile terminal device determines the validity of the assist information that has already been acquired. In this validity determination, when the acquired assist information is determined valid, the Autonomous positioning operation is performed based upon the positioning information received from the GPS satellite with the use of the acquired assist information, instead of acquiring the assist information from the network side once again.
On the other hand, when the acquired assist information is determined invalid, the A-GPS positioning operation is performed. The A-GPS positioning operation in this situation is performed in the following procedure. That is, firstly, a session is established with the network side. After the session establishment, the assist information is requested for the network side. As a response to the request, the assist information that is valid at the current time is acquired from the network side. Then, by use of the acquired assist information, the positioning operation is performed based upon the positioning information received from the GPS satellite.
The data of the positioning results acquired by performing the A-GPS positioning operation or the information on the fact that the positioning operation is impossible is notified to the network side. The session is released after this notification.
After that, while the above-described GPS positioning operation for continuously performing the GPS positioning operation on a regular basis is set as a basic GPS positioning operation, the GPS positioning operation is stopped when the acceleration sensor does not detect the continuous walking or when the mobile terminal device enters again the area where the already acquired in-area history is available. Then, the power consumption corresponding to the stopping in the positioning operation is suppressed by replacing the current positioning information with the already acquired positioning information.